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Medicines Q&As
Q&A 42.7
What are the equivalent doses of oral morphine to other oral opioids
when used as analgesics in adult palliative care?
Prepared by UK Medicines Information (UKMi) pharmacists for NHS healthcare professionals
Before using this Q&A, read the disclaimer at www.ukmi.nhs.uk/activities/medicinesQAs/default.asp
Date prepared: 5th November 2013
Background
Morphine is generally the strong opioid of choice for treating moderate to severe cancer pain (1) and a
common question is how to convert a dose of another opioid to morphine or vice versa. Other opioids
may be preferred, for example, if a patient obtains insufficient pain relief with morphine (or other strong
opioid) and/or is suffering severe adverse effects (1,2,3). However, switching to an alternative opioid is
only one approach to managing opioid adverse effects. Other strategies include (2):
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Reducing the dose of opioid (and possibly adding adjuvant analgesics).
Symptomatic management of the adverse effect(s).
Switching the route of administration.
If the strategies above have not worked, or are impractical, then a decision to convert to an alternative
opioid may be taken, preferably with advice from a palliative care or pain team.
Answer
Advice on opioid conversion
NB: Before using Table 1, read the notes below and the Limitations statement at the end of this
document.

Equivalent doses of opioids are given in Table 1. These are an approximate guide only because
comprehensive data are lacking and there is inter-individual variation (3). In addition, it should be
noted that sources differ in the equivalent doses they quote. Caution is required and careful
monitoring during conversion is necessary to avoid both underdosing and excessive dosing (3).

When converting from one opioid to oral morphine, or vice versa, the initial dose depends on the
relative potency of the two drugs (2,3) and route of administration (2). This Q&A deals only with
oral administration (see Table 1).

Some authors have suggested that, in most cases, the calculated dose-equivalent of a new drug
derived from e.g. Table 1 must be reduced to ensure safety. Based on clinical experience and
published guidelines, the starting point for dose reduction from the calculated equianalgesic dose is
25-50% (2,4,5). This dose reduction is particularly important when high doses are used (4). However,
the reduction may not be appropriate if the original opioid failed to control pain (see below). Reasons
for this suggested dose reduction include:
o
Incomplete cross-tolerance between opioid drugs, which would lead to effects (including
adverse effects) that would be greater than expected when a switch to a new drug is made (2).
1
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
o
There appears to be a large inter-individual variability in response (2).
o
There is a need to adjust for conditions that increase opioid risk (e.g. elderly patients, coexisting medical conditions) (4).
o
Most published opioid conversion tables have been derived from short-term studies in opioidnaive patients, which do not account for the influence of incomplete cross-tolerance between
opioids (2).
A dose reduction of at least 50% is recommended when switching at high doses (e.g. morphine or
equivalent doses of 1g/24 hours or more), in elderly or frail patients, or because of intolerable
undesirable effects (3). A similar dose reduction is recommended when there has been a recent
rapid escalation of the first opioid. ‘As required’ doses should be used to make up any deficit while
re-titrating to a satisfactory dose of the new opioid (3).

When considering opioid conversions, the severity of the pain should also be taken into account. For
example, if pain is not controlled by the current opioid then it may be appropriate to administer the
calculated equianalgesic dose of the new opioid (4).

The half-life of the two drugs needs to be considered when converting so that the patient does not
experience breakthrough pain or receive too much opioid during the conversion period.

The time to onset of action needs to be considered, for example, if moving from a non-modified
release to a modified release preparation. The timing of doses will therefore need to be carefully
considered.

The total daily dose of the current opioid(s), including all long-acting and breakthrough doses, must
be determined prior to conversion. If the patient is on multiple opioids, convert all to morphine
equivalents (see Table 1) (2).

Ensure that ‘as required’ doses of an opioid are prescribed for breakthrough pain (2,6). These should
not be modified release preparations or transdermal patches.

Once the conversion has occurred, the dose of new opioid should be titrated carefully according to
individual response (1,4) and the patient monitored closely for side effects and efficacy, especially
when switching at high doses (6). Careful monitoring is also particularly necessary when there has
been a recent rapid escalation of the first opioid (6). In selected patients who do not obtain a
satisfactory therapeutic outcome (improved pain relief or fewer adverse effects), further conversion to
a different opioid may be required (2,4).

Ensure naloxone is available.
2
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Table 1. Approximate equivalent potencies of oral opioids to oral morphine (see advice above).
Converting from another oral opioid to oral morphine:
Multiply the total daily dose of oral opioid by its potency equivalence to determine the equivalent total daily
dose of oral morphine.
Converting from oral morphine to another oral opioid:
Divide the total daily dose of oral morphine by the potency equivalence for the oral opioid which you are
converting to.
Oral Drug
(refs)
Duration of
action
(hours)
(standard
release
preparations)
Potency
equivalence
to
morphine
(oral to oral)
Notes
Buprenorphine (7,8)
6-8
80
(sublingual)
Care required as only one literature source suggests a
conversion (7) although this potency equivalence has
been cited for a number of years. No dose equivalence
studies comparing sublingual buprenorphine with oral
morphine have been published (8). Reports of
undesirable effects in patients switched to high doses of
buprenorphine (6-24mg/24h) (7).
Codeine (3,9-13)
3–6
0.08 - 0.1
Dihydrocodeine (3,9,12-14)
3-6
0.1
Hydromorphone (1,3,6,1113,15,16)
4-5
3.5 - 10
Morphine (3,17)
3-6
1
Oxycodone (1,3,11-13,1821)
3-6
1.5 - 2
Note high oral bioavailability compared to morphine
(18,19). One manufacturer advises a potency
equivalence of 1.5 - 2 with prolonged release
formulations, together with a 25-50% dose reduction
following conversion (20). Other manufacturers state an
approximate potency equivalence of 2 (19,21).
Not available
0.3 - 0.8
Manufacturer states that direct opioid conversion has not
been studied so potency equivalence has been
calculated indirectly. Manufacturer suggests an
analgesic potency equivalence of 0.4 - 0.8 (22).
Switching from another µ agonist (e.g. morphine) may
cause low-grade opioid withdrawal and as required
doses of the original opioid should be used to counter
this. Role of tapentadol in palliative care is unclear (3).
3–9
0.1 - 0.17
Manufacturer advises a potency equivalence of 0.1 0.17 (25).
Tapentadol (3,22)
Tramadol (3,11,13,23-25)
Codeine is partly metabolised to morphine (10).
Some sources suggest using a potency equivalence of 5
when converting from morphine to hydromorphone, and
using a potency equivalence of 4 if switching from
hydromorphone to morphine (15). The manufacturer
states an approximate potency equivalence of 5-10 (16).
3
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Equivalent potencies are only approximate and can be unpredictable. When converting from one
opioid to another, it is often appropriate to use a lower dose than the suggested equivalence
above. Close monitoring for side effects and efficacy is mandatory, especially at higher doses.
Example conversion:
Converting from morphine m/r 15mg bd to oral oxycodone:
 Total daily dose of morphine is 30mg.
 From Table 1, oxycodone potency equivalence = 1.5 – 2.
 Divide 30mg/1.5 = 20mg and 30mg/2 = 15mg.
 Therefore the approximate equivalent total daily dose of oral oxycodone is 15 - 20mg in
divided doses. See notes above on how this should be used in practice.
Limitations
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Evidence for the effectiveness of switching opioids when managing cancer pain or chronic noncancer pain is limited (1,4,26).
Considerable inter-individual differences exist in the pharmacokinetic and pharmacodynamic
behaviour of different opioids, so individual dose titration is essential (26).
Much of the dose equivalence information was derived from short term trials conducted in patients
with acute post-operative pain, or patients with cancer pain on low-dose opioids and therefore may
have limitations in applicability to repetitive administration and/or relatively high doses (4).
The studies that are available have differing patient populations, study methods and small sample
sizes. The duration of opioid exposure and the issue of tolerance are also factors in the interpretation
of data (27).
It has been suggested that the directional quality of cross tolerance may not be equal and has not
been fully explored. Ratios may change according to the direction of an opioid switch; however the
clinical relevance of this is not clear (27,28). Although it is unlikely to have a major impact when
switching at lower doses, it is possible that failure to recognise the directional difference may result in
negative consequences when switching at higher doses (28).
Dose conversion tables are not meant to provide recommended initiation doses for a given opioid or
patient (29).
Further trials are needed to optimise conversion ratios when switching from one opioid to another
(26).
The data presented are derived from adults and so may not be applicable to children.
Published data on opioid substitution therapy and combination preparations have been excluded.
References
1.
2.
3.
4.
5.
Caraceni A, Hanks G, Kaasa S et al for the European Palliative Care Research Collaborative
(EPCRC), on behalf of the European Association for Palliative Care (EAPC). Use of opioid
analgesics in the treatment of cancer pain: evidence-based recommendations from the EAPC.
Lancet Oncol 2012;13:e58-68.
Slatkin NE. Opioid switching and rotation in primary care: implementation and clinical utility. Curr
Med Res Opin 2009;25(9);2133-2150.
Twycross R, Wilcock A (eds).Strong opioids monograph. Updated October 2013. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
Fine PG, Portenoy RK. Establishing “best practices” for opioid rotation: conclusions of an expert
panel. J Pain Symptom Manage 2009;38(3):418-425.
Nuckols TK, Anderson L, Popescu I et al. Opioid prescribing: A systematic review and critical
appraisal of guidelines for chronic pain. Ann Intern Med 2014;160:38-47.
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Available through NICE Evidence Search at www.evidence.nhs.uk
Medicines Q&As
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Twycross R, Wilcock A (eds). Opioid dose conversion ratios monograph. Updated October 2013.
Palliative Care Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th
November 2013.
Twycross R, Wilcock A (eds). Buprenorphine monograph. Updated October 2013. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
Personal communication Medical Information Professional Information Ltd on behalf of Sandoz
Ltd (Tephine). 13th November 2013.
Twycross R, Wilcock A (eds). Weak opioids monograph. Updated June 2013. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
Twycross R, Wilcock A (eds). Codeine phosphate monograph. Updated October 2013. Palliative
Care Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
Wessex and ASWCS Palliative Physicians. The Palliative Care Handbook. Advice on clinical
management. 7th Edition. Countess Mountbatten House. Southampton University Hospitals.
October 2010:10.
Regnard C, Dean M (eds). A Guide to Symptom Relief in Palliative Care 6th edition. Radcliffe
Publishing. Oxford; 2010:67.
Pain management with opioids. Joint Formulary Committee. British National Formulary. London:
BMJ Group and Pharmaceutical Press. Accessed via http://bnf.org on 27th November 2013.
Twycross R, Wilcock A (eds). Dihydrocodeine tartrate monograph. Updated August 2012.
Palliative Care Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th
November 2013.
Twycross R, Wilcock A (eds). Hydromorphone monograph. Updated December 2011. Palliative
Care Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
SPC Palladone (hydromorphone) capsules. Napp Pharmaceuticals Ltd. Accessed via
http://www.medicines.org.uk/emc/ on 13th November 2013 (SPC last updated on the eMC: 25th
September 2009).
Twycross R, Wilcock A (eds). Morphine monograph. Updated October 2013. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
Twycross R, Wilcock A (eds). Oxycodone monograph. Updated May 2013. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
SPC OxyNorm (oxycodone) 5, 10, 20mg capsules. Napp Pharmaceuticals Ltd. Accessed via
http://www.medicines.org.uk/emc/ on 13th November 2013 (SPC last updated on the eMC: 27th
November 2008).
SPC Dolocodon (oxycodone) PR 10mg prolonged release tablets. Zentiva. Accessed via
http://www.medicines.org.uk/emc/ on 13th November 2013 (SPC last updated on the eMC: 10th
September 2013).
SPC Longtec (oxycodone) 5mg, 10mg, 20mg, 40mg, 80mg prolonged release tablets. Qdem
Pharmaceuticals Ltd. Accessed via http://www.medicines.org.uk/emc/ on 13th November 2013
(SPC last updated on the eMC: 25th June 2012).
Personal communication, Medical Information department Grünenthal Ltd. 13 th November 2013.
Twycross R, Wilcock A (eds). Tramadol monograph. Updated January 2012. Palliative Care
Formulary. Accessed via http://www.palliativedrugs.com/index.html on 14th November 2013.
SPC Zamadol capsules 50mg. Meda Pharmaceuticals. Accessed via
http://www.medicines.org.uk/emc/ on 19th December 2013 (SPC last updated on the eMC: 5th
December 2013).
SPC Zydol (tramadol) 50mg capsules. Grünenthal Ltd. Accessed via
http://www.medicines.org.uk/emc/ on 21st November 2013 (SPC last updated on the eMC: 5th
November 2013).
Vissers KCP, Besse K, Hans G et al. Opioid rotation in the management of chronic pain: where is
the evidence? Pain Practice 2010;10(2):85-93.
Berdine HJ, Nesbit SA. Equianalgesic dosing of opioids. J Pain Palliat Care Pharmacother
2006;20:79-84.
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28. Pereira J, Lawlor P, Vigano A et al. Equianalgesic dose ratios for opioids: a critical review and
proposals for long-term dosing. J Pain Symptom Manage 2001;22:672-687.
29. Anderson R, Saiers JH, Abram S et al. Accuracy in equianalgesic dosing: conversion dilemmas. J
Pain Symptom Manage 2001;21:397-406.
Quality Assurance
Prepared by
Kate Pickett, Medicines Q&A Pharmacist (based on earlier work by Louisa Rowlands and Anne Cole),
Wessex Drug and Medicines Information Centre, University Hospital Southampton NHS Foundation
Trust.
Date Prepared
5th November 2013
Checked by
Marc Miell (based on the Q&A checked by Dr Simon Wills and Sue Gough), Lead Medicines Information
Pharmacist, Wessex Drug and Medicines Information Centre, University Hospital Southampton NHS
Foundation Trust.
Date of check
27th May 2014
Search strategy
 Embase - search strategy: “opioid.af AND equivalence.af”
“(exp opiate agonist/ OR exp narcotic analgesic agent/ OR exp narcotic
agent/) AND equivalence.af (limited to H=Y and LG=EN)”
“(exp opiate agonist/ OR exp narcotic analgesic agent/ OR exp narcotic
agent/) AND exp bioequivalence/ (limited to H=Y and LG=EN)”

Medline - search strategy: “opioid.af AND equivalence.af”
“(exp analgesics, opioid/ OR exp narcotics/) AND exp therapeutic
equivalency/ (limited to H=Y and LG=EN)”
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Palliative Care Formulary. Accessed via http://www.palliativedrugs.com/index.html
Electronic Medicines Compendium. Accessed via / http://www.medicines.org.uk/emc/
NICE. Accessed via www.nice.org.uk
Palliative Care Guidelines Plus. Accessed via http://book.pallcare.info/
Cochrane Library. Accessed via http://www.thecochranelibrary.com/
NICE Evidence. Accessed via www.evidence.nhs.uk
SIGN Guidelines. Accessed via http://www.sign.ac.uk
European Association for Palliative Care. Accessed via http://www.eapcnet.eu/
American Pain Society. Accessed via www.ampainsoc.org
American College of Physicians. Accessed via www.acponline.org
Specialist textbooks
Personal communication Medical Information Reckitt Benckiser (Temgesic). November 2013
Personal communication Medical Information Grünenthal Ltd (Palexia). November 2013
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